Daily #4089

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4089

PERIOD COVERED: UT April 10, 2006 (DOY 100)

OBSERVATIONS SCHEDULED

ACS/HRC 10512

Search for Binaries Among Faint Jupiter Trojan Asteroids

We propose an ambitious SNAPSHOT program to survey faint Jupiter
Trojan asteroids for binary companions. We target 150 objects, with
the expectation of acquiring data on about 50%. These objects span
Vmag = 17.5-19.5, a range inaccessible with ground-based adaptive
optics. We now have a significant sample from our survey of brighter
Trojans to suggest that the binary fraction is similar to that which
we find among brighter main-belt asteroids, roughly 2%. However, our
observations suggest a higher binary fraction for smaller main-belt
asteroids, probably the result of a different formation mechanism
{evident also from the physical characteristics of the binaries}.
Because the collision environment among the Trojans is similar to that
of the Main Belt, while the composition is likely to be very
different, sampling the binary fraction among the fainter Trojans
should help us understand the collisional and binary formation
mechanisms at work in various populations, including the Kuiper Belt,
and help us evaluate theories for the origin of the Trojans.
Calibration of and constraints on models of binary production and
collisional evolution can only be done using these large-scale,
real-life physical systems that we are beginning now to find and
utilize.

ACS/HRC 10545

Icy planetoids of the outer solar system

Early HST studies of satellites of Kuiper belt object focussed on the
50-200 km objects that were the largest known at the time. In the past
3 years we have discovered a population of much more rare and much
larger {500-2000+ km} icy planetoids in the Kuiper belt. These objects
are the largest and brightest known in the Kuiper belt and, in the era
when we now know of more than 1000 Kuiper belt objects, these few
planetoids are likely to be the focus of much of the research on
physical properties of the outer solar system for years to come. We
are currently engaged in an intensive program involving Spitzer, Keck,
and other telescopes to study the physical and dynamical properties of
this new population. HST is uniquely capable of addressing one
parameter fundamental to completing the physical picture of these
planetoids: the existence and size of any satellites. The detection
and characterization of satellites to these large planetoids would
allow us to address unique issues critical to the formation and
evolution of the outer solar system, including the measurement of
densities, internal properties, sizes and shapes of these objects, the
study of binary formation as a function of primary size, and the
context of the Pluto-Charon binary. For these bright objects, a
satellite search takes less than a full orbit, allowing the
opportunity for a new project on UV spectroscopy of the planetoids to
piggyback at no added time cost. This poorly explored spectral range
has the potential to show unique signatures of trapped gasses,
cosmochemically important ices, and complex organic materials.

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/HRC 10625

A Multiwavelength Investigation of Comet 73P/SW3-C

The nucleus of comet 73P/Schwassmann--Wachmann~3 experienced a
non-tidal breakup in late 1995. The largest fragment {73P/SW3-C}
survived its subsequent perihelion passage in 2001 and will return in
2006, when it will pass very close to {0.08 AU} Earth. This represents
an outstanding opportunity to characterize a fresh cometary nucleus,
and we propose an intensive investigation using both the Hubble and
Spitzer telescopes. Employing the technique that our group has
developed over the past decade to characterize 31 cometary nuclei, we
will use HST/ACS to photometrically resolve the nucleus of 73P/SW3-C
at optical wavelengths and SST/MIPS to do the same thing at thermal
infrared wavelengths, thereby allowing us to determine both the size
and albedo of this fragment. We also plan to measure the lightcurve of
73P/SW3-C to obtain detailed shape information, and use HST/NICMOS to
probe the composition, in particular to search for evidence of icy
material on the fresh surface. Previous observations indicate that
most of the remaining mass of 73P/SW3 is in the form of numerous small
fragments. A few of those may have been captured by the C fragment,
and the determination of their orbits would allow the first, direct
measurement of the mass of a cometary nucleus. Thus, we will also
perform a deep search for any possible companions to the C-fragment.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

ACS/WFC 10587

Measuring the Mass Dependence of Early-Type Galaxy Structure

We propose two-color ACS-WFC Snapshot observations of a sample of 118
candidate early- type gravitational lens galaxies. Our lens-candidate
sample is selected to yield {in combination with earlier results} an
approximately uniform final distribution of 40 early-type strong
lenses across a wide range of masses, with velocity dispersions {a
dynamical proxy for mass} ranging from 125 to 300 km/s. The proposed
program will deliver the first significant sample of low-mass
gravitational lenses. All of our candidates have known lens and source
redshifts from Sloan Digital Sky Survey data, and all are bright
enough to permit detailed photometric and stellar- dynamical
observation. We will constrain the luminous and dark-matter mass
profiles of confirmed lenses using lensed-image geometry and
lens-galaxy structural/photometric measurements from HST imaging in
combination with dynamical measurements from spatially resolved
ground-based follow-up spectroscopy. Hence we will determine, in
unprecedented detail, the dependence of early-type galaxy mass
structure and mass-to-light ratio upon galaxy mass. These results will
allow us to directly test theoretical predictions for halo
concentration and star-formation efficiency as a function of mass and
for the existence of a cuspy inner dark- matter component, and will
illuminate the structural explanation behind the fundamental plane of
early-type galaxies. The lens-candidate selection and confirmation
strategy that we propose has been proven successful for high-mass
galaxies by our Cycle 13 Snapshot program {10174}. The program that we
propose here will produce a complementary and unprecedented lens
sample spanning a wide range of lens-galaxy masses.

ACS/WFC 10732

ACS internal CTE monitor

The charge transfer efficiency {CTE} of the ACS CCD detectors will
decline as damage due to on-orbit radiation exposure accumulates. This
degradation will be closely monitored at regular intervals, because it
is likely to determine the useful lifetime of the CCDs. All the data
for this program is acquired using internal targets {lamps} only, so
all of the exposures should be taken during Earth occultation time
{but not during SAA passages}. This program emulates the ACS
pre-flight ground calibration and post-launch SMOV testing {program
8948}, so that results from each epoch can be directly compared.
Extended Pixel Edge Response {EPER} and First Pixel Response {FPR}
data will be obtained over a range of signal levels for both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/WFC 10775

An ACS Survey of Galactic Globular Clusters

We propose to conduct an ACS/WFC imaging survey of Galactic globular
clusters. We will construct the most extensive and deepest set of
photometry and astrometry to-date for these systems reaching a main
sequence mass of ~0.2 solar mass with S/N = 10. We will combine these
data with archival WFPC2 and STIS images to determine proper motions
for the stars in our fields. The resultant cleaned cluster CMDs will
allow us to study a variety of scientific questions. These include
[but are not limited to] 1} the determination of cluster ages and
distances 2} the construction of main sequence mass functions and the
issue of mass segregation 3} the internal motions and dynamical
evolution of globular clusters, and 4} absolute cluster motions,
orbits, and the Milky Way gravitational potential. We anticipate that
the unique resource provided by the proposed treasury archive will
play a central role in the field of globular cluster studies for
decades, with a stature comparable to that of the Hubble Deep Field
for high redshift studies.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword 'USEAFTER=date/time' will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 10519

Testing the Stellar Coalescence and Accretion Disk Theories of Massive
Star Formation with NICMOS

The importance of massive stars cannot be underestimated - they
produce most of the heavy elements in the universe and dominate the
evolution of the interstellar medium in their vicinity. In spite of
their significance, our understanding of their formation is meager.
Both accretion through disks, analogous to the process of low-mass
star formation, and coalescence of low-mass stars through collisions
in the dense cores of stellar clusters have been suggested. Possibly
both mechanisms occur. High spatial resolution polarization
measurements of the closest massive young stellar objects {YSOs} will
enable us to search for evidence of disk accretion or coalescence in
the form of patterns indicative of light scattered off a coherent disk
or off a disk disrupted by an infalling star, respectively. Here we
propose to use 2 micron polarimetry with NICMOS to identify the
presence of accretion disks around massive YSOs or to characterize
their environments as possibly disrupted from a close stellar
encounter. There are only a few sources that meet the stringent
selection criteria for this investigation {even with HST}, which we
will examine here. High spatial resolution is required, but even more
important, the point spread function {PSF} must be stable with time.
Furthermore, the PSF must put minimal flux into large spatial scales,
something that cannot be achieved with adaptive optics. This
combination of high Strehl ratio and stable PSF can only be achieved
from space.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

10209 - GSacq(1,3,1) failed @ 100/15:01:47z

During LOS the GSacq(1,3,1)scheduled at 100/15:01:47 failed. At AOS
(15:15:15) the QSTOP and QF1STOPF were flagging. There were no other
flag indicating SRLEX or SSLEX. Also there were no ESB messages. The
map at 15:09:38 showed errors of V1=-0.06, V2=11.94, V3=-2.77,
RSS=12.26.

10210 - OBAD failed and GSacq failed @ 100/16:41:15z

OBAD 2 at 100/16:32:55 failed due to too few starts. ESB 1901 (OBAD
too few stars)was received. The GSacq(1,3,1) at 16:38:12 also failed.
Only QSTOP and QF1STOPF flagged out of limits.

10211 - FHST OBAD Failure, due to lack of sufficient stars @ 100/16:32:50z

OBAD scheduled at 100/16:32:50 using trackers 1 and 2 failed due to
insufficient percentage of stars identified. 486 ESB 1901
(OBAD_TOO_FEW_STARS) was received. OBAD success flag (mnemonic
GCHACLO9) remained at the same state. Subsequent acquisition failed
per HSTAR 10210.

10212 - FHST OBAD Failure @ 101/02:17:37z

OBAD scheduled at 101/02:14:48 using trackers 1 and 2 failed. ESB
message 1901 "OBAD_TOO_FEW_STARS" was received at 02:17:37. Subsequent
guide star acquisition was successful. OBAD tables 369 and 370 were
dumped in accordance with Ops Request 17543-2.

10214 - FHST OBAD Failure @ 101/05:23:13z

OBAD scheduled at 101/05:20:15 using trackers 1 and 2 failed. ESB
message 1901 "OBAD_TOO_FEW_STARS" was received at 05:23:13. Subsequent
guide star acquisition was successful. OBAD tables 369 and 370 were
dumped in accordance with Ops Request 17543-2.

10216 - FHST OBAD Failure @ 101/06:59:01z

OBAD scheduled at 101/06:56:10 using trackers 1 and 2 failed. ESB
message 1901 "OBAD_TOO_FEW_STARS" was received at 06:59:01. Subsequent
guide star acquisition was successful. OBAD tables 369 and 370 were
dumped in accordance with Ops Request 17543-2.

COMPLETED OPS REQUEST:
17543-2 - Dump OBAD tables after failed OBAD @ 101/02:24:25z,
101/05:27:26z, 101/05:44:30z, 101/07:03:53z, 101/07:17:45z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 14 12 (HSTAR 10209)
(HSTAR 10210)
FGS REacq 01 01

OBAD with Maneuver 30 26 (HSTAR 10211)
(HSTAR 10212)
(HSTAR 10214)
(HSTAR 10216)


SIGNIFICANT EVENTS: (None)